1. Field of the Present Invention
This application relates generally to motor vehicles, whether powered by gas, diesel, electric battery, propane, natural gas, or any other like material, and in particular to radiators and engines and preventing corrosion in the cooling system of said vehicles, especially those with components of dissimilar metal construction which present most cooling system corrosion problems.
2. Background
Automobile cooling systems circulate water and coolant liquids through an engine's water jacket, head, and water pump to facilitate heat transfer. After absorbing the heat, the hot liquid is piped back to the radiator/storage tank which is a liquid to air heat exchanger. A typical radiator is made up of a storage tank either above or to the side of the cooling tubes and exchanged cooling fins. This storage tank has an opening to the interior of the storage tank part, a core of cooling tubes, which is where the coolant liquid flows, and fins, connected to these cooling tubes, which transfer heat to the air that is pulled or pushed through the fins and around the tubes for heat transfer from the coolant to the air passing through.
Radiators and engines were historically made of iron, steel, copper, and/or brass, which, as similar metals, have little corrosion caused by electrolytic activity. Over time, however, aluminum parts have been incorporated into engine thermal control devices, such as radiators and heater cores. While the use of aluminum offers several advantages, an unfortunate side effect of using dissimilar metals is an increase in electrolytic activity, leading to increased vulnerability to corrosion. In response to the electrolytic activity, also known as electrolysis, aluminum components corrode and become porous and may begin to leak in as little as two weeks.
During electrolysis, one of the metals in the system acts as an anode and corrodes. The other metal acts as a cathode and does not corrode. Chemical corrosion inhibitors have been developed to inhibit electrolysis, but they are toxic, present problems to the environment, and present problems of disposal. Alternatively, sacrificial anodes, constructed of active metals, that is metals that react with oxygen, such as magnesium, aluminum, zinc or combinations thereof, have also been used as corrosion inhibitors. Sacrificial anodes do not eliminate the flow of electric current, but instead attract the electric current, acting as a “lightning rod” that electricity clings to, thus relieving the anodic metal of the thermal control device from the corrosive damage of electrolysis.
U.S. Pat. No. 5,292,595 describes a sacrificial anode of specified composition bonded to the core metal to prevent the occurrence of pitting corrosion of core material in a heat exchanger such as a radiator or heater core. Unfortunately such an anode is hard to access to check its condition or replace it when it wears out. A need exists for a corrosion-inhibiting sacrificial anode which is easily accessible. Since a sacrificial anode is designed to be consumed, easy accessibility would allow verification of its effective working status and efficient replacement when depleted.
Furthermore, prior attempts at preventing corrosion in heat exchangers have failed due to the sacrificial anode being installed in undesirable locations. U.S. Pat. No. 5,649,591 describes a sacrificial anode built into a radiator cap. Such a solution is imperfect because some radiators lack caps and, for those that do have caps, the position of the cap is too far from the inlet to effectively prevent corrosion from occurring.
Thus, a need continues to exist to prevent corrosion in radiators and other engine thermal control devices. Current sacrificial anode devices are deficient in that they fail to position the anode optimally to allow for maximal corrosion resistance and easy monitoring, removal, and replacement.